Chemokines are a family of structurally related small proteins released from a variety of different cells within the body (reviewed in Vinader et al, 2012, Future Med Chem, 4(7): 845-52). The name derives from their primary ability to induce chemotaxis and thereby attract multiple cells of the immune system to sites of inflammation or as a part of normal immune function homeostasis. Examples of the types of cells attracted by chemokines include monocytes, T and B lymphocytes, dendritic cells, natural killer cells, eosinophils, basophils and neutrophils. Chemokines, in addition to their primary role in inducing chemotaxis, are also able to cause activation of leukocytes at the site of inflammation—for example, but not limited to, causing degranulation of granulocytes, generation of super-oxide anions (oxidative burst) and up-regulation of integrins to cause extravasation. Chemokines initiate their biological activity through binding to and activation of cell surface receptors—chemokine receptors. Chemokine receptors belong to the G-coupled protein receptor (GPCR), 7-trans-membrane (7-TM) superfamily—comprising an extracellular N-terminus with 7 helical trans-membrane domains and an intracellular C-terminus. Traditionally, chemokines are considered to bind to their receptors in the 7-TM region—this binding leading to activation of the receptor and resulting in G-protein activation (and subsequent secondary messenger transmission) by the intracellular portion of the receptor.
CCR9 is a chemokine receptor shown to be expressed on circulating T lymphocytes (Zabel et al, 1999, J Exp Med, 190:1241-56) and, in contrast to the majority of human chemokine receptors, CCR9 currently has only a single ligand identified: CCL25, otherwise known as thymus-expressed chemokine (TECK) (Zabalos et al, 1999, J Immunol, 162: 5671-5). As CCL25 expression is limited to intestinal epithelium and the thymus (Kunkel et al, 2000, J Exp Med, 192(5): 761-8), this interaction has been demonstrated to be the key chemokine receptor involved in targeting of T lymphocytes to the intestine (Papadakis et al, 2000, J Immunol, 165(9): 5069-76). The infiltration of T lymphocytes into tissues has been implicated in a broad range of diseases, including, but not limited to, such diseases as asthma, rheumatoid arthritis and inflammatory bowel disease (IBD). Specific to IBD, it has been observed that CCR9+ CD4 and CD8 T lymphocytes are increased in disease alongside an increased expression of CCL25 that correlates with disease severity (Papadakis et al, 2001, Gastroenterology, 121(2): 246-54). Indeed, disruption of the CCR9/CCL25 interaction by antibody and small molecule antagonists of CCR9 has been demonstrated to be effective in preventing the inflammation observed in small animal models of IBD (Rivera-Nieves et al, 2006, Gastroenterology, 131(5): 1518-29 and Walters et al, 2010, J Pharmacol Exp Ther, 335(1):61-9). In addition to the IBD specific role for CCR9, recent data also implicates the CCR9/CCL25 axis in liver inflammation and fibrosis where increased expression of CCL25 has been observed in the inflamed liver of primary sclerosing cholangitis patients along with a concomitant increase in the numbers of CCR9+ T lymphocytes (Eksteen et al, 2004, J Exp Med, 200(11):1511-7). CCR9+ macrophages have also been observed in in vivo models of liver disease and their function proven with CCL25 neutralising antibodies and CCR9-knockout mice exhibiting a reduction in CCR9+ macrophage number, hepatitis and liver fibrosis (Nakamoto et al, 2012, Gastroenterol, 142:366-76 and Chu et al, 2012, 63rd Annual Meeting of the American Association for the Study of Liver Diseases, abstract 1209). Therefore, modulation of the function of CCR9 represents an attractive target for the treatment of inflammatory, immune disorder and other conditions and diseases associated with CCR9 activation, including IBD and liver disease.
In addition to inflammatory conditions, there is increasing evidence for the role of CCR9 in cancer. Certain types of cancer are caused by T lymphocytes expressing CCR9. For example, in thymoma and thymic carcinoma (where cancer cells are found in the thymus), the developing T lymphocytes (thymocytes) are known to express high levels of CCR9 and CCL25 is highly expressed in the thymus itself. In the thymus, there is evidence that the CCR9/CCL25 interaction is important for thymocyte maturation (Svensson et al, 2008, J Leukoc Biol, 83(1): 156-64). In another example, T lymphocytes from acute lymphocytic leukaemia (ALL) patients express high levels of CCR9 (Qiuping et al, 2003, Cancer Res, 63(19): 6469-77). While the role for chemokine receptors is not clear in the pathogenesis of cancer, recent work has indicated that chemokine receptors, including CCR9, are important in metastasis of tumours—with a potential therapeutic role suggested for chemokine receptor antagonists (Fusi et al, 2012, J Transl Med, 10:52). Therefore, blocking the CCR9/CCL25 interaction may help to prevent or treat cancer expansion and/or metastasis.
Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract in which tissue damage and inflammation lead to long-term, often irreversible impairment of the structure and function of the gastrointestinal tract (Bouma and Strober, 2003, Nat Rev Immunol, 3(7):521-533). Inflammatory bowel diseases may include collagenous colitis, lymphocytic colitis, ischaemic colitis, diversion colitis, Behçet's disease (also known as Behçet's syndrome), indeterminate colitis, ileitis and enteritis but Crohn's disease and ulcerative colitis are the most common forms of IBD. Crohn's disease and ulcerative colitis both involve chronic inflammation and ulceration in the intestines, the result of an abnormal immune response. Chronic and abnormal activation of the immune system leads to tissue destruction in both diseases, although ulcerative colitis is generally limited to the rectum and colon, whereas Crohn's disease (also known as regional ileitis) extends deeper in the intestinal wall and can involve the entire digestive tract, from the mouth to the anus.
Up to one million Americans have inflammatory bowel disease, according to an estimate by the Crohn's and Colitis Foundation of America. The incidence of IBD is highest in Western countries. In North America and Europe, both ulcerative colitis and Crohn's disease have an estimated prevalence of 10-20 cases per 100,000 populations (Bouma and Strober, 2003).
The primary goal when treating a patient with IBD is to control active disease until a state of remission is obtained; the secondary goal is to maintain this state of remission (Kamm, 2004, Aliment Pharmacol Ther, 20(4):102). Most treatments for IBD are either medical or surgical (typically only used after all medical options have failed). Some of the more common drugs used to treat IBD include 5-aminosalicylic acid (5-ASA) compounds (such as sulfasalazine, mesalamine, and olsazine), immunosuppressants (such as azathioprine, 6-mercaptopurine (6-MP), cyclosporine A and methotrexate), corticosteroids (such as prednisone, methylprednisolone and budesonide), infliximab (an anti-TNFα antibody) and other biologics (such as adilumumab, certolizumab and natalizumab). None of the currently available drugs provides a cure, although they can help to control disease by suppressing destructive immune processes, promoting healing of intestinal tissues and relieving symptoms (diarrhea, abdominal pain and fever).
There is a need to develop alternative drugs for the treatment of IBD, with increased efficacy and/or improved safety profile (such as reduced side effects) and/or improved pharmacokinetic properties. Treatment of IBD includes control or amelioration of the active disease, maintenance of remission and prevention of recurrence.
Various new drugs have been in development, including the aryl sulfonamide compound N-{4-chloro-2-[(1-oxidopyridin-4-yl)carbonyl]phenyl}-4-(1,1-dimethylethyl)-benzenesulfonamide, also known as Vercirnon or GSK1605786 (CAS Registry number 698394-73-9), and Vercirnon sodium. Vercirnon was taken into Phase III clinical development for the treatment of patients with moderate-to-severe Crohn's disease. Vercirnon is the compound claimed in U.S. Pat. No. 6,939,885 (Chemocentryx) and is described as an antagonist of the CCR9 receptor. Various other aryl sulfonamide compounds have also been disclosed as CCR9 antagonists that may be useful for the treatment of CCR9-mediated diseases such as inflammatory and immune disorder conditions and diseases; for example, see the following Chemocentryx patent applications, WO2004/046092 which includes vercirnon, WO2004/085384, WO2005/112916, WO2005/112925, WO2005/113513, WO2008/008374, WO2008/008375, WO2008/008431, WO2008/010934, WO2009/038847; also WO2003/099773 (Millennium Pharmaceuticals), WO2007/071441 (Novartis) and US2010/0029753 (Pfizer).
Thus a number of CCR9-modulating compounds are known and some are being developed for medical uses (see, for example, the review of CCR9 and IBD by Koenecke and Förster, 2009, Expert Opin Ther Targets, 13 (3):297-306, or the review of CCR antagonists by Proudfoot, 2010, Expert Opin Investig Drugs, 19(3): 345-55). Different classes of compounds may have different degrees of potency and selectivity for modulating CCR9. There is a need to develop alternative CCR9 modulators with improved potency and/or beneficial activity profiles and/or beneficial selectivity profiles and/or increased efficacy and/or improved safety profiles (such as reduced side effects) and/or improved pharmacokinetic properties.
We now provide a new class of compounds that are useful as CCR9 modulators and in particular as partial agonists, antagonists or inverse agonists of CCR9. The compounds of the invention may have improved potency and/or beneficial activity profiles and/or beneficial selectivity profiles and/or increased efficacy and/or improved safety profiles (such as reduced side effects) and/or improved pharmacokinetic properties. Some of the preferred compounds may show selectivity for CCR9 over other receptors, such as other chemokine receptors.
Such compounds may be useful to treat, prevent or ameliorate a disease or condition associated with CCR9 activation, including inflammatory and immune disorder diseases or conditions such as inflammatory bowel diseases (IBD).